Hi sarahb and welcome to the forum
You would need to discuss this with your Supervisor, however you can generally miss up to three monthly payments without disturbing the voluntary arrangement.
If you needed to take a longer payment break, then the Supervisor should consider whether to approach your creditors and formally vary the terms of the arrangement to take the period of non-payment into account. This could only be done by holding another meeting of creditors, where they would vote either in favour of or to reject your revised proposals.
Generally, this is usually acceptable for up to six months, but you should expect to see the IVA term extended accordingly. Any longer, and then I feel the creditors might see the IVA as no longer viable.
Hope this helps - are you already in an IVA?
Regards, Melanie Giles, Insolvency Practitioner for over 20 years.
For further details contact me at
http://melaniegiles.com and view my IVA blog at:
http://melaniegiles.blogs.iva.co.uk