A slightly different approach - the payload is too BIG

All the helpful answers so far deal with increasing the payload limit. But it might also be the case that the payload is indeed too big but for no good reason. If there's no valid reason for it to be, consider looking into why it's so bloated in the first place.

Our own experience

For example, in our case, an Angular app was greedily sending an entire object in the payload. When one bloated and redundant property was removed, the payload size was reduced by a factor of a 100. This significantly improved performance and resolved the 413 error.