There is a limit to the number of Guild Coins you can hold in your inventory. The base amount is 2,000, but there are guild perks that can increase that further.
If you've hit your maximum capacity, it's time to buy some guild crates! Use the Buy 5 to get a 10% discount, and it guarantees chips for the featured hero!
Please note that you will be able to collect Guild Coins from guild check-in and quests, even if you are at max. Those coins will be lost, so be sure to check your totals frequently!