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License Error 0xC004C020

0xC004C020 and 0xC004C021: Your MAK Has Run Out of Activations

11 min read Updated October 5, 2026 Windows Activation & Licensing

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Microsoft publishes 0xC004C020 as the activation server reporting that a Multiple Activation Key has exceeded its limit, and 0xC004C021 as the extension limit having been exceeded too. For both, the documented resolution is the same: request more activations from the Microsoft Licensing Activation Centers.

Run these on the failing machine, in an elevated Command Prompt

slmgr /dli
slmgr /dlv
  1. Confirm the machine is actually on a MAK rather than a volume client key. If it is a volume client, this is the wrong article.
  2. Read the remaining count. In VAMT, use Refresh product key data online; your volume licensing portal reports the same figure.
  3. If seats remain and this machine still fails, the pool is not the problem: retype the key with slmgr /ipk and retry slmgr /ato.
  4. If the pool is empty, contact the Microsoft Licensing Activation Centers and ask for more activations. That is Microsoft’s documented resolution for both codes.
  5. Stop activating machines against the key while you wait. Every further success spends a seat you may want for something else.

Do this before buying anything. Microsoft’s published resolution for 0xC004C021 is the same as for 0xC004C020, so the extension code is not automatically the end of the road.

If the count goes up and the machine activates, you are done. If the request is refused, the next section covers where the seats went and how to stop it recurring.

Why it happens

A Multiple Activation Key is one key with a fixed number of permanent activations behind it. There is no host, no lease and no renewal, which is exactly why it suits laptops, isolated networks and small sites. The trade-off is arithmetic: a MAK cannot activate more machines than it was sold for, and the count is held centrally where nothing you run locally can adjust it.

Microsoft’s published text for 0xC004C020 is that the activation server reported the Multiple Activation Key has exceeded its limit, and for 0xC004C021 that the extension limit has been exceeded. The listed resolution for both is to request more activations from the Microsoft Licensing Activation Centers so that the limit, or the extension limit, is increased. That is worth reading carefully, because a good deal of advice treats the second code as a dead end and Microsoft does not.

The count is per activation, not per machine, and that distinction is where most estates lose track. Reimaging a machine spends another seat. Cloning a virtual machine from a template that already carries the key spends one per clone. Significant hardware changes can present as a new activation. Seats are not returned when a machine is decommissioned, so a fleet that gets rebuilt each year exhausts a MAK far faster than its headcount suggests.

0xC004C015 is reported in the same conversations and Microsoft publishes no meaning for it, as is the case for 0x803FA07F and 0x803FA080. It is worth being blunt about that last pair: there is a widespread habit of treating any 0x803FA0-something as the Settings-app twin of a matching 0xC004C-something, and Microsoft’s own error list does not support it. Where 0x803FA067 is listed, it sits with the invalid-key and servers-busy group rather than with the code it is usually paired with.

You have deployed every seat you bought

You have this one if The remaining count reads zero and the number of machines on the key roughly matches what you were sold.

  1. Count the machines that legitimately need to stay activated on this key.
  2. Ask the Microsoft Licensing Activation Centers for additional activations, with that number and the reason ready.
  3. If the request is refused, order additional seats against your agreement before deploying anything further.
  4. Install the key on new machines only in their final configuration, not during build and test.

Reimaging and cloning have burned the pool

You have this one if The consumed count is far higher than your machine count, and the estate is rebuilt regularly or deployed from templates.

  1. Remove the product key from the reference image and generalise it with sysprep /generalize so each deployment starts without one.
  2. Activate at the end of deployment rather than baking activation into the image.
  3. Move machines that are rebuilt more than once a year to KMS or Active Directory-Based Activation, where activation renews rather than being spent.
  4. Keep MAK for the devices that genuinely live off the network.

This is the structural fix. More seats without a change to the deployment process buys time rather than a solution.

The key has spread beyond its intended scope

You have this one if Machines you do not recognise are on the key, or several teams were handed the same one with no record of who deployed what.

  1. Use VAMT to inventory which machines are activated against the key.
  2. Move anything outside the intended scope onto its own key or onto volume activation.
  3. Request a fresh key for the remaining estate if the current one has circulated widely.
  4. Store the key in a licensing record rather than in a build document everyone can read.

The key does not belong to this product at all

You have this one if The count looks healthy and activation fails anyway, because the key was issued for a different edition or product family.

  1. Check what the key was issued for in your licensing portal.
  2. Confirm the edition on the machine with DISM /Online /Get-CurrentEdition.
  3. Install the MAK that matches, then run slmgr /ato.
  4. If no matching MAK exists on your agreement, that is a purchasing question rather than an exhausted pool.

Full reference

Reading the count without guessing

Where to look What it tells you
VAMT, after Refresh product key data online The remaining activation count Microsoft holds for the key
Your volume licensing portal The same figure, plus what the key was issued for
slmgr /dli on a machine Which key that machine is on, and its channel. Not the pool size
slmgr /dlv on a machine The same with more detail, including licence status
The activation error itself 0xC004C020 means the limit; 0xC004C021 means the extension limit as well

A failed activation does not consume a seat. Only a successful one does, which is why the advice while a pool is exhausted is to stop attempting activations you do not need rather than to worry about the ones that have already failed.

What each route can and cannot do

Route What it achieves
Retrying on the client Nothing. The count is not held locally
Reinstalling the key, or rebuilding the licence store Nothing, for the same reason
Telephone activation Checks the same central count and returns the same answer
Microsoft Licensing Activation Centers Can increase the limit or the extension limit. This is the documented resolution for both codes
Moving machines to KMS or Active Directory-Based Activation Stops future rebuilds consuming seats. Does not restore spent ones
Ordering additional seats The remaining route once Microsoft declines an increase

Stopping the pool draining again

  1. Take the key out of the reference image and generalise it with sysprep /generalize. slmgr /rearm resets activation timers and is called by sysprep during that operation.
  2. Activate at the end of deployment, once the machine is in its final configuration.
  3. Decide which machines belong on MAK at all. The honest list is usually shorter than the deployed one.
  4. Move the rest to KMS if they stay on your network, or to Active Directory-Based Activation if they are domain-joined.
  5. Record every activation against a machine name, so the next conversation with Microsoft starts from evidence rather than memory.

Choosing between MAK and the renewing options

MAK and KMS are not two prices for the same thing. Both rest on licences you hold under the same agreement; what differs is how activation is delivered. KMS suits machines that stay on your network and get rebuilt often, because activation renews instead of being consumed, and it needs 25 client machines or 5 servers contacting the host before it will answer anything. Active Directory-Based Activation suits domain-joined estates of any size and has no threshold at all. MAK suits machines that are none of those things.

Most estates that run out of MAK seats are running MAK on machines that had no need of it. Sorting that out is worth more than the seats, because it is the only version of this that does not recur.

Codes that arrive here from somewhere else

Code What Microsoft publishes Where that leaves you
0xC004C020 The MAK has exceeded its limit Request more activations, then buy if refused
0xC004C021 The MAK extension limit has been exceeded The same documented resolution. Not automatically the end
0xC004C003 The activation server determined the key is blocked A different problem. No count will help
0xC004C008 The key could not be used – already on another device, or a host key past 10 activations on 6 computers Read carefully which of the two applies to you
0xC004C001 The key is invalid Check the key before checking the pool

When a licence is the actual fix

Ask Microsoft first. The published resolution for both 0xC004C020 and 0xC004C021 is to request more activations from the Microsoft Licensing Activation Centers, and that costs nothing but a phone call and the evidence of how the seats were spent. Where that request is declined, additional seats really are the fix and no configuration change substitutes for them. Arco supplies additional Windows 11 Enterprise MAK seats against your agreement, and will look at your machine count alongside your seat count to say whether part of the estate belongs on KMS or Active Directory-Based Activation instead of in a larger MAK pool. What no reseller can do is raise the count on a key you already hold; only Microsoft can do that.

Every code this article covers

Code What it points at Source
0xC004C020 The activation server reported that the Multiple Activation Key has exceeded its limit. Documented resolution: request more activations from the Microsoft Licensing Activation Centers Microsoft Learn
0x803FA07F Reported by some machines in the same situation. Microsoft publishes no meaning for it, and no source pairs it with a specific 0xC004C code not published by the vendor
0xC004C021 The activation server reported that the Multiple Activation Key extension limit has been exceeded. Same documented resolution as 0xC004C020 Microsoft Learn
0x803FA080 Seen alongside the extension refusal. No published meaning not published by the vendor
0xC004C015 Another activation-server refusal in the same area. No published meaning; read it with the remaining count in front of you not published by the vendor

Confirm the fix worked

  1. Refresh product key data online in VAMT, or your licensing portal, shows the remaining count reflecting the activations you were granted or the seats you added.
  2. On a previously failing machine, slmgr /ato completes without an error.
  3. slmgr /dli on that machine reports Licence Status: Licensed on a MAK channel.
  4. The key is out of the reference image, and a freshly deployed machine activates at the end of the build rather than during it.
  5. Re-check the count after a deployment cycle and confirm it falls at the rate you expect.

Questions people ask about this

Can I free up seats by removing the key from retired machines?

No. Seats are consumed at activation and are not returned when a machine is wiped, retired or has its key removed. This is the single most common misunderstanding about MAK, and it is why rebuild-heavy estates run out early.

Will Microsoft increase the count if I ask?

It is the documented resolution for both codes: request more activations from the Microsoft Licensing Activation Centers so the limit, or the extension limit, is increased. Whether a particular request is granted depends on your agreement and the reason, so have the machine count and an explanation ready.

Is KMS cheaper than buying more MAK seats?

They are not alternative prices for the same thing. Both draw on licences you hold under the same agreement; what differs is how activation is delivered. KMS suits machines that stay on your network and get rebuilt often. MAK suits machines that do not.

Does a failed activation consume a seat?

No. Only a successful activation does. That is why the advice while a pool is exhausted is to stop attempting activations you do not need.

What is the difference between 0xC004C020 and 0xC004C021?

The first says the key’s limit has been reached; the second says an extension limit has been reached as well, which means an increase has already been applied at some point. Microsoft publishes the same resolution for both, so the second is not automatically a dead end.

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